Pneumatic Tire

Abstract

A pneumatic tire is provided with, in the tread surface, land portions that include a rib or a plurality of blocks. The land portions are provided with a plurality of narrow shallow grooves and a plurality of recessed portions in a contact patch. Additionally, the opening area ratio Sc of the recessed portions in the central portion region in the tire lateral direction of one continuous contact patch and the opening area ratio Se of the recessed portions in the end portion regions in the tire lateral direction have the relationship Se<Sc, where the central portion region is defined as the region in the central portion in the tire lateral direction occupying 50% of the continuous contact patch of the land portions, and the end portion regions are defined as the regions in the left and right end portions in the tire lateral direction occupying 25%.

1 . A pneumatic tire comprising in a tread surface thereof a land portion that comprises a rib or a plurality of blocks, wherein
 the land portion comprising in a contact patch thereof a plurality of narrow shallow grooves and a plurality of recessed portions, and   an opening area ratio Sc of the recessed portions in a central portion region in a tire lateral direction of one continuous contact patch in the land portion and an opening area ratio Se of the recessed portions in end portion regions in the tire lateral direction have a relationship Se<Sc, where   the central portion region is defined as a region in a central portion in the tire lateral direction occupying 50% of the continuous contact patch, and the end portion regions are defined as regions in left and right end portions in the tire lateral direction occupying 25%.   
     
     
         2 . The pneumatic tire according to  claim 1 , wherein the opening area ratio Sc of the recessed portions in the central portion region in the tire lateral direction and the opening area ratio Se of the recessed portions in the end portion regions in the tire lateral direction have a relationship 1.50≦Sc/Se. 
     
     
         3 . The pneumatic tire according to  claim 1 , wherein a disposal number Nc of the recessed portions in the central portion region in the tire lateral direction and a disposal number Ne of the recessed portions in the end portion regions in the tire lateral direction have a relationship Ne<Nc. 
     
     
         4 . The pneumatic tire according to  claim 3 , wherein the disposal number Nc of the recessed portions in the central portion region in the tire lateral direction and the disposal number Ne of the recessed portions in the end portion regions in the tire lateral direction have a relationship 1.50≦Nc/Ne. 
     
     
         5 . The pneumatic tire according to  claim 1 , wherein a disposal density Da of the recessed portions in an entire region of the one continuous contact patch is in a range 0.8 unit/cm 2 ≦Da≦4.0 unit/cm 2 . 
     
     
         6 . The pneumatic tire according to  claim 1 , wherein
 the land portion comprises in the contact patch thereof a plurality of sipes, and   the recessed portions are disposed spaced apart from the sipes.   
     
     
         7 . The pneumatic tire according to  claim 6 , wherein
 the plurality of sipes are disposed side by side in a tire circumferential direction and divide the land portion into a plurality of sections, and   at least one of two discretionary adjacent sections of the plurality of sections comprises the recessed portions in the central portion region in the tire lateral direction.   
     
     
         8 . The pneumatic tire according to  claim 6 , wherein
 the plurality of sipes are disposed side by side in a tire circumferential direction and divide the land portion into a plurality of sections, and   three discretionary sections adjacent in the tire circumferential direction of the plurality of sections comprise a section comprising the recessed portion in the central portion region in the tire lateral direction and a section comprising the recessed portion in either of the end portion regions in the tire lateral direction.   
     
     
         9 . The pneumatic tire according to  claim 6 , wherein
 the plurality of sipes are disposed side by side in a tire circumferential direction and divide the land portion into a plurality of sections, and   three discretionary sections adjacent in the tire circumferential direction of the plurality of sections comprise a section with the recessed portion and a section without the recessed portion.   
     
     
         10 . The pneumatic tire according to  claim 1 , wherein
 the land portion is a row of blocks that comprises a plurality of blocks, and   the recessed portions are disposed in corner portions of the blocks.   
     
     
         11 . The pneumatic tire according to  claim 1 , wherein
 the land portion is a row of blocks that comprises a plurality of blocks, and   the recessed portions are not disposed in end portions of the blocks in a tire circumferential direction or a central portion region of the blocks in the tire lateral direction.   
     
     
         12 . The pneumatic tire according to  claim 1 , wherein the opening area of the recessed portions ranges from 2.5 mm 2  to 10 mm 2 . 
     
     
         13 . The pneumatic tire according to  claim 1 , wherein the recessed portions have a circular or elliptical shape at the contact patch of the land portion. 
     
     
         14 . The pneumatic tire according to  claim 1 , wherein a wall angle α of the recessed portions is in a range −85 degrees≦α≦95 degrees. 
     
     
         15 . The pneumatic tire according to  claim 1 , wherein a depth Hd of the recessed portions and a groove depth Hg of the narrow shallow grooves have a relationship 0.5≦Hd/Hg≦1.5. 
     
     
         16 . The pneumatic tire according to  claim 1 , wherein at least one of the recessed portions is disposed at a position corresponding to a vent hole of a tire mold. 
     
     
         17 . The pneumatic tire according to  claim 1 , wherein an average value Ac of the opening area of the recessed portions in the central portion region in the tire lateral direction and an average value Ae of the opening area of the recessed portions in the end portion regions in the tire lateral direction have a relationship Ae<Ac. 
     
     
         18 . The pneumatic tire according to  claim 17 , wherein the average value Ac of the opening area of the recessed portions in the central portion region in the tire lateral direction and the average value Ae of the opening area of the recessed portions in the end portion regions in the tire lateral direction have a relationship 1.5≦Ac/Ae≦4.0. 
     
     
         19 . The pneumatic tire according to  claim 17 , wherein
 the land portion comprises a plurality of types of the recessed portions with differing opening areas, and   70% or more of the recessed portions disposed in the central portion region in the tire lateral direction have a larger opening area than an average value of the opening area of the recessed portions disposed in the continuous contact patch.   
     
     
         20 . The pneumatic tire according to  claim 17 , wherein
 the land portion comprises a plurality of types of the recessed portions with differing opening areas, and   the recessed portions with an opening area smaller than the average value of the opening area of the recessed portions disposed in the continuous contact patch are disposed on an outermost side of the continuous contact patch in the tire lateral direction.   
     
     
         21 . The pneumatic tire according to  claim 17 , wherein
 the land portion comprises a plurality of sipes that are disposed side by side in a tire circumferential direction and that divide the land portion into a plurality of sections, and a plurality of types of the recessed portions with differing opening areas, and   the recessed portions with an opening area larger than the average value of the opening area of the recessed portions disposed in the continuous contact patch are disposed in at least one of three discretionary sections adjacent in the tire circumferential direction of the plurality of sections.   
     
     
         22 . The pneumatic tire according to  claim 17 , wherein
 the land portion is a row of blocks comprising a plurality of blocks and comprises a plurality of types of the recessed portions with differing opening areas, and   the recessed portions with an opening area smaller than the average value of the opening area of the recessed portions disposed in the continuous contact patch are disposed in corner portions of the blocks.   
     
     
         23 . A pneumatic tire comprising in a tread surface thereof a land portion comprising a plurality of blocks,
 the land portion further comprising in a contact patch thereof a plurality of narrow shallow grooves and a plurality of recessed portions, and   an opening area ratio Sc′ of the recessed portions in a central portion region in a tire circumferential direction of one continuous contact patch and an opening area ratio Se′ of the recessed portions in end portion regions in the tire circumferential direction have a relationship Se′<Sc′, where   the central portion region is defined as a region in a central portion in the tire circumferential direction occupying 50% of the continuous contact patch, and the end portion regions are defined as regions in front and back end portions in the tire circumferential direction occupying 25%.   
     
     
         24 . The pneumatic tire according to  claim 23 , wherein a disposal number Nc′ of the recessed portions in the central portion region in the tire circumferential direction and a disposal number Ne′ of the recessed portions in the end portion regions in the tire circumferential direction have a relationship Ne′<Nc′. 
     
     
         25 . The pneumatic tire according to  claim 23 , wherein an average value Ac′ of the opening area of the recessed portions in the central portion region in the tire circumferential direction and an average value Ae′ of the opening area of the recessed portions in the end portion regions in the tire circumferential direction have a relationship Ae′<Ac′.